Worlds Collide: Art history and materials science in Yucatán

In the summer of 1991, 13-year-old Amara Solari set off on a more than 3,000-mile family trip from the Napa Valley in California to the Yucatán Peninsula in Mexico. In a rented Volkswagen bus, Solari, her parents and her sister toured the tropical destination that would become not only an enduring source of wonderment and discovery, but eventually the focal point of Solari's academic research.

For the last five years, Solari, now professor of art history and anthropology at Penn State, has led a research team on an historical and, unexpectedly, scientific journey in the Yucatán.

Working closely with colleague Linda Williams of the University of Puget Sound, she has scoured the peninsula to identify, document, interpret and analyze murals painted inside churches by Maya Christian artists more than 400 years ago, combining art history and cutting-edge materials science in the only known cohesive study of these fragile artworks.

Solari's affinity for the Yucatán resurfaced shortly after she earned a bachelor's degree in anthropology in 2000 from the University of California, Berkeley. She spent a couple of field seasons after graduation on archaeological digs in Honduras, but her thoughts kept drifting back to that family trip and a place she still felt connected to.

For Solari, the history of the colonial era, which began in 1521 when Hernándo Cortés and a ragtag group of Spanish conquistadors invaded the Aztec empire and ended in 1821 with Mexican independence from Spain, always had an appeal - and she was specifically interested in the conversations through art between the Indigenous Maya people and the Spaniards who oversaw the campaigns to convert them to Catholicism.

"The Yucatán Peninsula is perfect for an art historian who wants to study those moments of interaction," Solari said. "Unlike other areas of Latin America, largely because of a lack of modern economic growth, Yucatecan architecture and its associated artworks have remained like a time capsule of the 16th century."

A working bond in the Yucatán

Over the last 20 years, Solari has explored the history of this cultural crossroads. She has authored or co-authored six books, been published in numerous journals and delivered dozens of lectures on her research. In 2010, soon after she was contacted by Williams to speak at a conference, a partnership was born.

"I read one of her first articles and was absolutely thrilled to see that there was anyone, let alone another art historian, working on that time period in Yucatán," remembered Williams, a specialist in 16th and 17th-century Mexico. "There just aren't that many of us."

The connection opened endless research possibilities, and the two eventually focused on the murals: initially 22 artistic treasures that Solari and Williams had both observed resurfacing piece by piece from behind centuries-old plaster. Each research trip revealed a more complete view of the paintings that told a visual story of Spanish and Maya cultural interaction and the development of Mexican Catholicism.

After finally meeting at the conference, the two developed a working bond that evolved into a sisterhood, with dreams of writing a book that would finally offer to the world and, perhaps more importantly, to Indigenous Mayas themselves, a comprehensive account of the religious, cultural and historical importance of the murals.

That dream became a reality when the duo submitted a grant proposal to the National Endowment for the Humanities in 2018. The following year, their project, "Maya Christian Murals of Yucatán: Indigenous Catholicism in Early Modern New Spain," was awarded $200,000, the highest amount allocated to research in the humanities.

Maya murals hidden under plaster

The towns and villages of the Yucatán vary widely in size and level of economic development, but one common characteristic is the imposing presence of colonial churches, built by Indigenous stonemasons in the 16th century at the direction of Spanish Franciscan friars. These churches were and are the town centers, and the murals their showpieces.

Using vibrant blue, green, yellow and red pigments, all locally sourced and used by native artists for centuries, the artworks featured Christian iconography: Images of Christ, the Virgin Mary and various saints depict the central tenets of early modern Catholicism and were used as a tool of evangelization.

"The Counter-Reformation is in full swing by the end of the 16th century, the very moment when these murals are created," Solari explained. "The Protestants are accusing the Catholics of idolatry for venerating the same kind of images that are being used in these indigenous missions."

By the 18th century, these murals had been systematically covered under plaster whitewash by clergymen eager to alter the aesthetic of the churches and, Solari said, to simplify their Christian messages.

The whitewash was enduring. Over the last 30 years, however, by a combination of tropical climate and human intervention, the plaster has begun to peel, gradually revealing the murals beneath. The size and quality of the exposed artworks vary from brightly colored scenes that cover an entire wall to a single fragment of the Virgin Mary that is barely visible. Since the project began, Solari and Williams have discovered mural cycles in three additional churches, bringing the total from 22 to 25. According to Solari, there are likely dozens more.

Today, the churches continue to be used for baptisms, marriages and Sunday services, but most of the townspeople don't even know the murals are there, says Claudia García-Solís, a conservator and restorer assigned to the project by the Instituto Nacional de Antropología e Historia (INAH), the agency tasked with preservation of Mexican cultural heritage. For García-Solís, this highlights the importance of the project.

"It is incredibly meaningful to have and share a record of these paintings," she said. "Preservation is ideal, but explaining and understanding their relevance, even for the people of the Yucatán, is very important for Mexico."

Exploring the village churches of the Yucatán

As the cultural significance of the research became clear, Solari said she knew that capturing the work with digital photography and video would be an essential preservation component of the project.

She was familiar with Yale's Center for the Study of Material and Visual Cultures of Religion (MAVCOR), an open-access collection of high-resolution media documenting religious, cultural and archaeological sites around the world. Through the center's website, Solari connected with editor and curator Emily Floyd.

With Floyd and her technical ability on board, an intensive research trip was scheduled for April 2018. The goal was to visit churches in the villages of Maní, Tabí, Izamal, Temax and Dzidzantún, all located in the northern Yucatán, and to gather digital images, videos and, perhaps most importantly, small fragments of the murals for materials analysis.

Having what Solari calls "the dream team" in place, she, Williams and Floyd flew to the Yucatán, rented a car, filled it with gear, "loaded up on Cheez-its and Coca Cola," said Solari, and went to work.

As they entered each town, the team would seek out the sacristan to gain access to the church while Floyd prepped her recording gear. One piece of equipment always caught the attention of the local children: the DJI Phantom 4 Pro drone she used to capture aerial images of the church and its surroundings.

"They would all gather around as I explained what it is and what it does," Floyd remembered.

For one busy week, the team traveled church to church, logging 8- to 10-hour days to gather dozens of hours of footage, hundreds of photos, and fragments of pigment for analysis.

Using a scalpel, García-Solís deliberately excised from nondescript sections of the murals, careful to maintain their integrity. The removal of samples, which are about the size of a pin head, was a tedious process requiring multiple government permits.

This legal framework for sampling murals is well-defined in Mexico. "These tiny fragments are rightfully deemed cultural patrimony and it is thus usually illegal to remove them the country," Solari said. However, for García-Solís and INAH, Penn State's international research reputation and its advanced technological capabilities created a natural partnership that she said is beneficial to Mexico's preservation efforts.

Protecting the artifacts is of paramount importance, said Solari. Simply cleaning a mural with the wrong product can cause a chemical reaction that could destroy the painting. Even more difficult can be choosing the right sealant to protect against deterioration.

The only way to guarantee safe interaction with the murals, the team realized, is to identify the materials used in their creation. That's where Penn State's Materials Characterization Lab (MCL) comes in. Housed within the Materials Research Institute at Penn State, MCL is a world-class facility offering state-of-the-art scientific analysis of materials samples.

"This process can be very expensive, and the one thing that INAH doesn't have much of is money," García-Solís said. "This relationship with Amara and Penn State presented an opportunity to safely preserve these paintings."

After the successful first trip, the team returned to the Yucatán three more times on fragment-gathering missions, with the final one coming in March of 2020.

Throughout that fateful week, the team, like much of the world, began to hear news reports about the spread and severity of a virus named COVID-19, adding a sense of urgency to their work. At week's end, with ample data and samples gathered, Solari nervously boarded a plane for the journey home, one of the last flights before the U.S. closed its borders to international travel.

Art history meets materials science

A few days after her return, Penn State announced that all international travel was on hold indefinitely, clouding the future of the project.

"For an art historian, the next step would have been to travel to Seville, Spain, and the Archive of the Indies to research the Mexican colonial documents," Solari explained. "The archive is where any correspondence sent from the colonies back to Spain was collected and housed."

The inability to gather textual information that could help to date the murals and tell their story caused her to shift her focus and become more dependent on the scientific analysis, a task she said was not only out of her comfort zone, but "completely foreign."

Solari delivered the collection of mural fragments to the MCL, where Nichole Wonderling, X-ray scattering manager, and Julie Anderson, research technologist, invited her to take part in the analysis.

Wonderling's goal was to find traces of the clay mineral palygorskite, which when heated together with indigo creates the pigment known as "Maya blue." The process dates back to A.D. 300 and the pigment, which is virtually impervious to time and weather, was commonly used in the Yucatán throughout the Colonial period.

Using the lab's X-ray diffractometer, Wonderling and assistant research professor Beth Last explored the samples in what they call a "hunt and peck" mission. The process proved difficult at first because of the presence of calcite in the plaster attached to the paint, but after employing a more focused microdiffraction technique, they found what they were looking for.

Anderson has since been using an electron microscope to scan the fragments. To determine the chemistry of the pigments used, she has worked with Energy Dispersive Spectrometry. The lab employed an ion milling process to remove the top amorphous layer from the fragments and reveal a pristine sample surface. This has allowed the team to analyze cross sections to eliminate the intrusion of materials that could have been added later to alter a mural or add a protective layer.

Throughout the analysis, Wonderling said that Solari has been a welcome addition to the team, her keen interest a breath of fresh air.

"She was just so excited about what we were doing and mesmerized with what was possible," Wonderling said. "It was fun to work with her, and I hope this success can let that person who maybe isn't comfortable with science and technology know that there are people here who can help them."

The power of collaboration

So far, the MCL's findings have allowed Solari and Williams to declare with certainty that all the murals they have sampled were created during the Colonial period, using not only Maya blue, but also yellow and red ochres and carbon black. As the research continues, Solari expects to confirm the origins of additional murals, thanks in part to the pigment analysis, she said.

"We've been able to basically reconstruct the entire Colonial palette because of these samples," Solari said. "I just keep thinking, 'this is the power of collaboration at Penn State.'"

She and Williams are writing that long-planned book, expected to be completed in 2022. In the meantime, Floyd and the MAVCOR team have created "Colonial Maya Churches of the Yucatán," a stunning, high-resolution, 360-degree online tour of the churches and their murals, available on the MAVCOR website.

Additional work on the samples combined with post-pandemic access to the Archive of the Indies will likely result in more discoveries. The scientific data will aid García-Solís and INAH as they devise proper cleaning and preservation methods. For Solari, however, these data open up an even larger interpretation.

"The science can tell me that this pigment is composed of 'x' and then we determine that 'x' does not come from Yucatán. In determining its place of origin, I am able to reconstruct an entire economic network premised upon the movement and exchange patterns of native people," Solari explains. "By illuminating the contours of daily life in the colonial period, we're revealing the agency of Indigenous actors during this historical moment and beyond."

There's another, more personal, dimension for Solari as well. In December of 2021, she returned to the Yucatán for a research trip, this time with a new research assistant - her 5-year-old daughter, Catalina.

The days spent driving through the Yucatán on bumpy jungle roads were a little sweeter this time, Solari said. Some of the usual art-hunting gear was replaced by a car seat and a new research assistant who adds a whole new perspective to her work.

"This is my favorite area of the world," Solari said. "My parents brought me here when I was a girl and because of that, I know it's important to share it with my own child. The amazing thing is, she absolutely loves it."

This story first appeared in the Fall 2022 issue of Research/Penn State magazine.